Prime Minister Rishi Sunak has said “racism stings” in response to a slur used against him by a Reform UK canvasser, which Nigel Farage has refused to apologise for and denounced as a “political set up”.

Campaigners for Mr Farage’s party Reform UK were recorded making racist comments, including about the Prime Minister who is of Indian descent.

The footage, made by an undercover Channel 4 reporter, showed Reform campaigner Andrew Parker using the racist term about Mr Sunak and suggesting migrants should be used as “target practice”.

Another canvasser described the Pride flag as “degenerate” and suggested members of the LGBT community are paedophiles.

During a written Q&A from users on parenting forum Mumsnet, Mr Sunak was asked: “Do you think Nigel Farage is racist?”

The Prime Minister replied: “Racism stings. I’ve experienced it in the past and I’ve spoken about this recently.

“But I’m also your Prime Minister running the country two generations after my grandmother emigrated here, leading the most diverse Cabinet in history, and the fact that neither of these things are a big deal tells you Britain is a great country and we have lots to be proud of.

“With regards to Farage, I won’t put labels on people, but I will call out blatant racism when I see it, and there are clearly deep, deep problems in the party he leads.

“To know my girls may have heard their dad be called a “f****** P***” by someone campaigning for Reform is shocking. We are better than that as a country.”

During his stint on Question Time, Mr Farage repeated claims that Mr Parker is an actor and he described the expose as “a political set-up of astonishing proportions”.

He said: “Let me tell you, from the minute (Mr Parker) turned up in that office in Clacton and I saw him, he was acting from the very start. He even says on his website, ‘hire me, I do undercover filming’.

He added: “This is a total and utter set-up that has been leapt on, of course, by our political opponents, leapt on by most of the mainstream media.”

Asked who he believed paid Mr Parker to pretend to be a Reform canvasser, Mr Farage said: “It may well have been the production company, or it’s the guy himself who wanted publicity to get more parts, I don’t know. What I know is this is a political set-up of astonishing proportions.”

But Mr Parker told the PA news agency that his volunteering for Reform was separate from his acting job, adding that he had been “goaded” into making the comments caught on camera.

Channel 4 hit back at the claims Mr Parker was a paid actor, with a spokesperson for the broadcaster saying: “We met Mr Parker for the first time at Reform UK party headquarters, where he was a Reform party canvasser.”

On Friday evening, Mr Farage faced incisive live questioning from audience members about the remarks made, as one said he employed “a whole slew of massive racists” and another called on the Reform leader to “take responsibility for your actions and say ‘sorry’, and stop making excuses?”

In response to the former, Mr Farage said: “I’m not going to apologise. I’m not going to apologise – for what? And we’ll find out the full truth, but I promise you what happened over the weekend, what was on the front page of The Times today is a set-up, a deliberate attempt to smear us. When you look at it, what do you say? It’s almost unbelievable.”

A spokesman for Essex Police said the force is “urgently assessing” the comments “to establish if there are any criminal offences”.

Labour leader Sir Keir Starmer said he was “shocked” by the “clearly racist” footage and that the Reform UK leader faces a “test of leadership”.

Business Secretary Kemi Badenoch said Reform candidates were the “offcuts” from other parties as she urged Reform voters to “come back” to the Tories.

In an interview with The Times, she said: “People do need to look at them. It goes well beyond racism, misogyny. It’s people who are not fit to make the decisions about your life.

“They don’t understand what it’s about. They’ve got no clue. I think that (Mr Farage) wants to be talked about again. This is all a big show for him. Nigel Farage doesn’t care if there’s a Labour government.

“This is I’m A Celebrity for Nigel Farage. He’s done I’m A Celebrity, came third, he wants to see if he can come first or second in politics, which is just another game [to him], but actually this is about people’s lives.

“I really want Reform voters to know that we’ve heard you. We understand. But you need to come back to the Conservative Party.”

On Question Time, Mr Farage was read racist or xenophobic comments made by Reform candidates, including Leslie Lilley, candidate for Southend East & Rochford; Edward Oakenfull, candidate for Derbyshire Dales; and Robert Lomas candidate for Barnsley North.

Mr Farage said: “In most cases, they’ve been disowned. People like (Leslie) Lilley, honestly, what he said is criminal.”

When asked: “So why is he your candidate?”

Mr Farage said: “I have no idea”, prompting laughter from the audience.

He said: “I inherited this. It was a start-up party. I paid a professional London vetting company to weed this out. The work wasn’t done.”

Asked if he would withdraw support from the three referenced candidates, Mr Farage said: “I wouldn’t want anything to do with them.”